This invention relates to pumps of the type used for introducing controlled amounts of a reagent into a process stream. These devices are typically referred to as chemical injectors and are used in a variety of manufacturing facilities for introducing metered amounts of fluid into another fluid stream, typically small amounts of a reagent into a process stream. One such chemical injection system is shown in U.S. Pat. No. 4,370,996, which system includes a gas powered timing relay and an injector pump, with the timing relay providing gas under pressure at controlled intervals for actuating the pump. Typically the pumps are controlled by such timing relays, and one such relay is shown in said U.S. Pat. No. 4,370,996, and another timing relay is shown in U.S. Pat. No. 4,465,090.
The reagents with which the injector pumps are used often are highly toxic or caustic or corrosive material, and often have strong odors. The caustic and corrosive materials tend to damage the pumps and hence it is desirable to avoid any contact between the reagent and the pump mechanism. Also, it is desirable to avoid leakage of the toxic materials and materials with strong odors, as well as leakage of the caustic and corrosive materials. In general, two types of pumps have been used in the past.
In one type of pump, the process stream is introduced into a pump chamber through a first check valve and exits from the pump chamber through a second check valve, with the pumping action being obtained by a positive displacement plunger which reciprocates in the pump chamber. With this type of construction, the plunger is in direct contact with the reagent, and seals are provided about the plunger for limiting leakage of the reagent along the plunger into the pump mechanism. High pressure seals are required in this type of pump, with a high back pressure in order to reduce the leakage. However, the reagent being in direct contact with the seals severely limits the effective operating life of the seals.
Typical pumps of this type include the Williams Instrument Company, Inc. Chemical Injector Models P250D and P500D and the Morgan Products Chemical Injector Models 50DS through 550DS.
Another type of injector pump or controlled volume pump utilizes an impermeable diaphragm between the pump plunger and the pump chamber, with movement of the pump plunger or piston causing movement of the diaphragm and hence obtaining the pumping action. Since this is a positive displacement type of pump, some type of bypass configuration is required in order to obtain the diaphragm displacement without damage to the diaphragm. This is achieved in existing pumps by means of a complex fluid bypass passage and valve system.
One such configuration is shown in U.S. Pat. No. 3,149,469, and one such diaphragm pump is produced by the Milton Roy Company as a Controlled Volume Pump.
It is an object of the present invention to provide a new and improved injector pump which will pump metered amounts of fluid for introduction into a process line, which pump incorporates a diaphragm or other impermeable member isolating the pumped material from the pump mechanism. A further object of the invention is to provide such an injector pump which is operable with the impermeable member without requiring any fluid bypass valving configuration for obtaining pump operation.
It is a further object of the invention to provide such an injector pump which can utilize various types of impermeable members, including diaphragms, bellows and Bourdon tubes. An additional object is to provide such an injector pump which can be operated with a single gas pressure inlet, or with dual gas pressure inlets for reciprocating motion, or with mechanical type drives.
Other objects, advantages, features and results will more fully appear in the course of the following description.